Add in CGMMSEO solver (Xining Du)

[kostrzewa]

Xining Du has done some work to the CGMMS solver to make it compatible with EO preconditioning:

"Basically I was using the CG solver with evenodd preconditioning, and I did some modifications (I call it CGMMSEO) to let it solve multiple masses one by one. The reason I did this was that I found it is faster than the CGMMS solver without evenodd preconditioning."
"The code I have been using is the tmLQCD version 5.1.6. However, I did some modifications on top of it, mainly reorganizing the CGeo solvers for multiple masses in a single solver. The basic solver routines are not changed."

It would be good to merge these changes back into the general code.